بررسی عددی و تجربی مقاومت خمشی پیچ تیتانیوم Ti6Al4V در استخوان فمور
محورهای موضوعی : فرآیندهای شبیه سازیعلی فتی 1 , پیمان مشهدی کشتیبان 2 *
1 - استادیار، گروه مهندسی مکانیک، دانشکده فنی و مهندسی، دانشگاه هرمزگان، بندرعباس
2 - دانشیار، دانشکده مهندسی مکانیک، دانشگاه صنعتی ارومیه، ارومیه
کلید واژه: المان محدود, تست خمش, استخوان فمور,
چکیده مقاله :
پیچ های ارتوپدی که جهت اتصال ایمپلنت های ارتوپدی استفاده می شوند، همیشه نقش مهمی در افزایش استحکام و مقاومت در برابر شکست استخوان دارند. بدون پیچ، استفاده از بسیاری وسایل ثابت کننده مانند صفحات استخوانی، ناخن های داخل مدولاری و حتی برخی از پروتزهای رایج کمتر موثر و یا حتی غیرممکن خواهد بود. هنگام کاربرد و بعد از بستن ایمپلنتها، پیچ‌های تحت فشار، تحت انواع بارهای خمشی، کششی یا فشاری قرار می‌گیرند و نتیجتا در جهت بارهای وارده باید تغییر فرم الاستیک در محدوده مجاز داشته باشند. جهت بررسی دقیق عملکرد پیچ، در این کار مقاومت خمشی پیچ ارتوپدی تیتانیوم به روش اجزای محدود بررسی شد و نتایج به‌دست‌آمده با آزمایش‌های تجربی مقایسه و تایید شد. رفتار پیچ در آزمایش خمش از نظر تنش، نیرو و جابجایی مورد بحث قرار گرفت. مقایسه نتایج ماکزیمم نیرو نشان دهنده تفاوت 16 درصدی بین شبیه سازی و کار عملی در بارگذاری خمشی است. از آنجایی که لنگر خمشی نیروهای بیشتری را به نواحی بیرونی وارد می‌کند، این نتیجه حاصل شد که سطح استخوان حداکثر تنش را در نازک‌ترین قسمت رزوه داخلی نشان می‌دهد. به دلیل ناپیوستگی اتصال رزوه پیچ با استخوان، در ناحیه بسته شده پایین، مقدار تنش بالایی در نوک پیچ رخ می دهد. مشابه قسمت رزوه دار بالایی، حداکثر مقادیر تنش برای استخوان نیز در بخش بالا قرار می گیرد.
Orthopedic screws, which are used to connect orthopedic implants, always play an important role in increasing strength and resistance to bone fracture. Without screws, the use of many fixation devices such as bone plates, intramedullary nails and even some common prostheses will be less effective or even impossible. During application and after closing the implants, screws under pressure are subjected to various bending, tensile or compressive loads, and as a result, they must have an elastic deformation within the permissible range in the direction of the applied loads. In order to accurately check the performance of the screw, in this work, the bending strength of the titanium orthopedic screw was investigated using the finite element method, and the results obtained were compared and confirmed with experimental tests. The behavior of the bolt in the bending test was discussed in terms of stress, force and displacement. Comparing the maximum force results shows a 16% difference between simulation and practical work in bending loading. Since the bending moment exerts more forces on the outer regions, it was concluded that the bone surface shows the maximum stress in the thinnest part of the inner thread. Due to the discontinuity of the connection of the screw thread with the bone, in the lower closed area, a high amount of stress occurs at the tip of the screw. Similar to the upper threaded part, the maximum stress values for the bone are also located in the upper part.
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